Macroscopic theory of pulsed laser annealing

Radiation from high-power Q-switched lasers has been used recently in semiconductor research to anneal the lattice damage caused by ion implantation, diffuse surface-deposited dopant films, recrystallize doped amorphous films deposited on substrates, and remove precipitates present after conventional high-temperature dopant diffusion. All of these processes can be understood in terms of models based on macroscopic diffusion equations for heat and mass transport, cast in a finite-difference form to allow for the temperature- and spatial-dependence of the thermal conductivity, absorption coefficient, reflectivity, and other quantities. Results of calculations on silicon with the models show that the near-surface region of a sample can melt and stay molten for times of the order of 100 nsec during which dopant diffusion in the liquid state and nonequilibrium segregation during ultrarapid recrystallization are sufficient to explain the major features of the experimental results. Brief descriptions of the physical and mathematical models and some of the results obtained with them are given, with particular emphasis on segregation effects